Plumb bob



J. l. ROOSE May 6, 1947.

PLUMB B OB Filed Jan. 16, 1945 INVENTOR. JOHN R0055 ATTORNEYS Patented May 6, 1947 UNITED STATES PATENT OFFICE PLUMB BOB John I. Roose, Los Angeles, Calif.

Application January 16, 1945, Serial No. 573,039

1 Claim.

This invention relates to improvements in. plumb bobs.

An object of the invention is to provide an improved plumb bob on which there is a reel mounted for rotation about an axis located in a vertical plane coincident with the center of gravity of the plumb bob and having a tubular screw through which the suspension line that is adapted to be wound upon the reel may extend. This screw is designed to be tightened against the reel to lock the reel against rotation in any adjusted position so that the length of the suspension line that is paid out from the reel can be easily and quickly adjusted in the plumb bob to meet various requirements.

Another object of the invention is to provide an improved plumb bob having the above mentioned characteristics which is so designed that it will hang true.

With the foregoing and other objects in view, which will be made manifest in the following detailed description and specifically pointed out in the appended claim, reference is had to the accompanying drawings for an illustrative embodiment of the invention, wherein:

Fig. 1 is a view in side elevation of the improved plumb bob.

Fig. 2 is a vertical section taken substantially upon the line 2-2 upon Fig. 1.

Referring to the accompanying drawings wherein similar reference characters designate similar parts throughout, the improved plumb bob comprises a suitable body 10 preferably cylindrical in general shape and having a, conical lower end II. A pointed block I2 completes the conical bottom of the body and serves to close the entrance to a chamber IS in the lower end of the body that is designed to receive mercury. The use of a hollow chamber filled with mercury can be dispensed with although the use of a mercury loaded plumb bob is generally regarded as desirable. In the upper end of the body there is a diametrically extending opening I4 through which extends a spindle l5. A reel I6 is rotatably mounted on the spindle and is adapted to have the suspension line I! wound thereon. A tubular screw i8 is threaded into the top of the body so that its axis is in the same vertical plane with the axis of the spindle l and the center of gravity of the plumb bob. The bore l9 that extends axially through the screw is of a size which permits the suspension line H to merely slide freely therethrough without any excessive clearance, and this screw preferably has a knurled head 20 by which the screw may be screwed downwardly through the body to engage the convolutions or turns of the suspension line wound upon the reel.

The operation and advantages of the improved plumb bob are as follows: The free or upper end of the suspension line may be adapted to any suitable support that it is desired to plumb. By backing 011 the screw I8 the reel is permitted to freely rotate on the spindle l5 and the required length of suspension line can thus be withdrawn through the hollow screw. When the desired length of line has been withdrawn the screw may be tightened downwardly against the portions of suspension line that remain wound on the reel. This locks the reel against rotation at a point where the desired length of suspension line has been withdrawn. As the axis of the screw and the axis of rotation of the reel and the center of gravity of the body II] are in the same vertical plane the plumb bob will hang true with the point Of the closure [2 disposed vertically below the point from which the suspenson line I! is suspended. This is true regardless of the fact that the portion of the line which extends upwardly through the screw I8 is withdrawn from one side of the reel. The length of the screw plus the fact that there is no excessive clearance between the line and the interior of the screw will thus cause the plumb bob to hang true. The improved plumb bob is very advantageously used where the upper end of the line is suspended from a point a considerable distance above the surface over which the point of clearance I2 is desired to be suspended. Under these circumstances the screw Hi can be loosened and tightened to free and lock the reel to secure a very accurate adjustment of the amount of suspension line withdrawn.

Various changes may be made in the details of construction without departing from the spirit and scope of the invention as defined by the appended claim.

I claim:

A plumb bob having a transverse slot therein, a reel rotatably mounted in the slot for rotation about a horizontal axis that intersects the vertical axis of the hob, and a tubular screw threaded into the top of the bob having its lower end extending into the slot and through which the line unwound from the reel extends, the screw being arranged coaxially with the vertical axis of the bob and being adapt-ed to be screwed down into engagement with the line remaining on the reel to hold the reel against rotation.

JOHN I. ROOSE.

REFERENCES CITED Ihe following references are ofrecord in the of this patent:

UNITED STATES PATENTS Nu ber Name Date 1,274,662 Armour Aug. 6, 1918 1,076,569 Gambllee Oct. 21, 1913 

